Electronic code pulse receiving circuit



W. H. T. HOLDEN ELECTRONIC CODE PULSE RECEIVING CIRCUIT March 31, 1953 Filed Oct. 17, 1950 4 Sheets-Sheet l ATTORNEY AAAA v4 Sheets-Sheet 2 com v W. H. T. HOLDEN ELECTRONIC CODEPULSE RECEIVING CIRCUIT March 3l, 1953 Filed oct. 17, 195o vUhu.

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ELECTRONIC CODE PULSE RECEIVING CIRCUIT Filed'oct. 17, 195o 4 sheets-sheet s /Nl/wroR W H. 7.' HOLDEN Wdh/M ATTORNEY March 31, 1953 Fild oct. 17, i950 w. H. T. HOLDEN ELECTRONIC CODE PULSE RECEIVING CIRCUIT 4 Sheets-Sheet 4 um INH L* mm s E5 v #e /NVENTOR By n4 H. rHoLof/v l C). )H

ATTORNEY Patented Mar. 31, 1953 .ELECTRONIC CODE PULSE `RECEIVING CIRCUIT William H. 'L Holden, Pasadena, Calif., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., va corporation `of New York Application October 17, 1950, Serial No. 190,493

2 Claims. l

This invention relates to telephone :systems and has for lits object `improvementin the reception and registration ci ldesignations 'in such systems.

The use of multifrequency pulses for the transmission of .designations between offices `is well known. In the sending of such 'pulses two `frequencies are sent out simultaneously and are separated at the receiving oice vby means of lters tuned to the various frequencies which feed into individual detectors which `in turn control registers.

`One diiculty experienced with receiving such pulses is in controlling the strength of the signals as fed to the detectors.

In accordance with `the present invention means is provided responsive to kthe signal strength for varying the sensitivity of the detectors.

More specically, each lter operates into av high impedance full Wave rectier, arranged to deliver a negative and a positive output. All positive outputs are combined and operate to 'increase the positive grid -bias of the detectors, While the individual negative outputs are applied to the grids of these same detectors.

These features of the invention will be more clearly understood Afrom a consideration of the following description in connection 'with the drawings, in which:

Fig. 1 is a schematic showing of a telephone system in which the present 'invention may be used;

' Fig. 2 shows the receiving iilters and detectors.

Fig. A3 shows a set of registers on which received designations are stored.

Fig. 4 shows a steering circuit, and

Fig. 5 shows the manner in which Figs. 2 to 4 should be arranged.

Reference may be made to the patent to A. J. Busch, No. 2,585,904, granted February 19, 1952,

for a complete telephone system to which the The marker translates that part of the desi'gna-v tion identifying the oflice in which the wanted line is located and selects a trunk |05 outgoing to that oihce. Having also determined that the oflice is one requiring alternating-current code pulses, the marker selects a suitable sender, transfers the line designation to the digit storing relays |02 `of the selected sender .and operates the trunk connector |03 to connect the sender vwith the selected trunk. The marker then connects with :and operates .the line link switches |04 .and trunk link .switches |05 to connect the :callingline with the trunk .and releases.

'The seizure of trunk |06 causes the `register connector I 01 to connect anincomingregister including the equipment shown with trunk |06.

When the register is ready .to receive pulses, it

causes the `trunk supervisory `.circuit |08 at `the called oice to transmita signal over trunk |06 which is repeated by the trunk supervisory circuit |00 at the calling oflice to the sender.

'In response to this signal, the digit steering chain l| I0 functions to 'successively enable those two of the oscillators which have been selected by the digit Astorage 'relays |02, the enabled oscillator transmitting alternating current over pulsingcircuit |2 which has been extended to the receiving equipment vof the register at the wanted oice. `It may be noted that the talking circuit is held disconnected Yfrom the trunk during the designation transfer by vmeans of `the trunk splitting circuits ||3 and ||4.

In the register, `the alternating-current code signals are `received by a limiting amplifier H5, tuned lters H6, `rectiiiers H1 and `detectors ||8 which selectively operate the registers H9 which are successively rendered responsive bythe steering chain |20. Each designation Lis preceded by a vstart signal which operates start circuit 112| to initiate the operation of the steering chain |20, the steering chain |20 being advanced in vresponse to the reception of each digit under the control of the chain advance circuit |22. Following the last digit an end signal is sent which operates the end circuit |23.

The end circuit 23 in turn operates marker connector |24 which connectsan idle marker |25 with the register, whereupon the `registered designation is transferred to the `marker |25 which in turn connects with and operates trunk link switches |26 and line link switches |21 to connect trunk |00 with the wanted subscribers line |28. The trunk splitting .circuits I3 and I4 now operate to disconnect the sender and register and complete the talking connection lbetween substations |00 and |28. Ringing and supervision take place in the Well-known manner.

A suitable register for generating and transmitting the multifrequency pulses is shown in" When the register of the present invention has been selected, it is connected with the incoming trunk by means of a register connector 200, which also operates oli-normal relay 20|. Relay 201 locks under the control of release relay 262 and connects -l-130-volt battery to conductor 203 to prepare the tubes for operation. The trunk conductors are extended by the register connector 200 to a two-stage limiter amplier 204 of the push-pull type, the output of which is fed through transformer 205 to a set of lters 206 to 212. Filters 206 to 21| are band-pass lters designed to pass frequencies of 700 cycles, 900 cycles, 1100 cycles, 1300 cycles, 1500 cycles and 1'700 cycles, respectively. Filter 212 is a balancing lter used to improve the transmission characteristics of the circuit.

The output of each ampliiier is connected to a full Wave rectier, comprising two rectifier elements, the output of amplierEBB, for example,

being connected to a rectier made up of elements 213 and 214.

Rectifier 214 is so poled that the negative half waves pass to the grid of detector 215. Rectier 213 is poled to pass the positive half waves and is connected, in parallel, with the corresponding recters belonging to the other filters 20? to 21 i to the grid of tube 22|.

The grid of each detector is connected over conductor 222 to ground through resistance 223 detector, for example detector 215, the now of current through that detector is cut oir so that the potential cn the anode, which is connected through resistance 224 to conductor 203 tends to rise to +130 Volts. However, this potential is held to +105 volts by connecting the anode through a limiter rectifier 2215 to a source of +105 volts provided by voltage regulator tube 226 and resistance 221 connected to the +130-v volt supply conductor 203.

An individual diode, 228, 229, etc., is also connected between the anode of each detector and 4S-volt battery through resistance 233 which has a value of 100,000 ohms. When a signal is received by detector 215 the voltage at thecathode end of diode 220 changes from -20 volts to +50 volts approximately and this voltage -is applied through resistance 234 to the grid of the register chain advance triode 235, causing current to flow through tube 235.

The anode of tube 235 is connected through a 50,000-ohm resistance 236 to conductor 203 and through another 50,000-ohm resistance 23T to the control anode of tube 238 which is used to operate the steering chain of Fig. 4.

Each register of Fig. 3 comprises ve gas-nlled tubes, one for each of the detectors. Register 300, for example, includes tubes 301 to 305, corresponding respectively to detectors 215 to 220. Each tube is similarly arranged. For example, tube 30| has its main gap connected between ground through a register relay 350 and +130 volts on conductor 203. The control anode is connected through a l-rnegohm resistance 351 to the output of the corresponding detector 215 over conductor 239 and through a second l-rnegohm resistance 352 over conductor 413 to the cathode of the corresponding steering tube 40| which is normally connected to ground through resistance 411. A grounded condenser 353 is also connected to the control anode to absorb surge voltages.

The rst pulse to reach the register is a start pulse made up of frequencies of 1700 cycles and 1100 cycles. Detectors 2|1 and 220 are cut oi and the Voltage on output conductors 24| and 244 rises as above described to volts. Tube 235 becomes conducting but the register tube 303 is not affected since its control anode is grounded. Output conductors 241 and 244 are connected through rectiers 245 and 246 in parallel to conductor 241 and the control anode of tube 400. Tube 400 becomes conducting and its cathode assumes a potential of .+60 Volts, which is applied through resistance 410 to the control anode of tube 40 1.

It may be noted that the rectiers 245 and 246 are so arranged that although the potential on conductor 24| may rise in response to digit registration, the lower potential on conductor 244 prevents tube 400 from reoperating falsely.

When the start pulse ends, tube 235 Will be cut oi and tube 238 operates, causing the potential on conductor 248 to rise, charging condenser 412 to a potential which in combination with the potential supplied through resistance 4|0 causes tube 40| to break down and extinguishes tube 400. With tube 401 conducting, the cathode voltage rises to +60 volts which is applied over conductor 4E3 to the control cathodes of tubes 30| to 305 through individual 1-rnegohm resistances such as resistance 352 and to the control anode of tube 402.

Assuming that the first digit is three, the correl sponding digit pulse will cause tubes 216 and 211 to be blocked and the potential on conductors 240 and 24| will rise to +105 volts so that the potential on the control anodes of tubes 302 and Chain Tube Cathode Signal Detector Anode Register Control Voltage Voltage Cathode Voltage 0 40 20 60 (chain tube on) 40 50 0 105 (signal present) 52. 5 60 (cham tube on) 105 (signal present) 82.5 (operate) Tube 235 also conducts fully and lowers the voltage on the starter anode of tube 238 below the sustaining voltage so that tube 238 is extin guished.

At the end of the pulse, tube 235 is cut oi and tube 230 ionized to cause the ionization of chaintube 402 and prepare the tubes of register 310.'

'I 'ube 401 is deionized at this time. In a manner similar to that above'described, each of the incoming digits is registered.

Following the last digit an end signal is re` ceived which is received by detectors 219 and 220, causing the potential on conductors 243 and 244 to rise to +105 volts. These conductors are connected through rectifiers 249 and 250 to conductor 25| to cause the ionization of tube 409 and the operation of relay 414.

Relay M4 grounds conductor 415 to initiate the operation of the marker control circuit 410 which operates the marker connector 4H to connect the register with the marker and transfer the registration to the marker. When the marker has completed its functions it connects ground through the marker connector to conductor 410, operating relay 202. Relay 202 opens the locking circuit of relay 20| which releases, removing +130-vo1t battery from conductor 203 to restore the pulse receiving and digit registration circuits to normal.

What is claimed is:

1. In a rtelephone system, an incoming circuit, alternating-current signals comprising a plurality of frequencies applied to said incoming circuit, a plurality of lters connected to said incoming circuit, each lter tuned to one of said signal frequencies, a plurality of detector tubes one connected to each of said filters, and means 'to render said detectors independent of the strength of said signals including a pair of oppositely poled rectiers connected to each of said zilters, one rectier of each pair included in the connection between one lter and one detector, 'the other rectiers of each pair connected in multiple to an auxiliary voltage limiter, and means to conneet said auxiliary voltage limiter to each of said detectors in opposition to said one rectifier.

2. In a telephone system, an incoming circuit, alternating-current signals comprising a plurality of frequencies applied to said incoming circuit, each filter tuned to one of said signal frequencies, a plurality of detector tubes one connected to each of said filters, each of said tubes having a pair of output electrodes and a grid electrode, registering circuits connected to the output electrodes, means for providing a normal bias for said grids, means to render the output circuit of said detectors independent of the strength of said signals including a pair of oppositely poled rectifiers connected to each of said lters, one rectifier of each pair included in the connection between one lter and one detector and poled to pass the negative half cycles of said frequencies, the other rectiers of each pair being poled to pass the positive half cycles of said frequencies and connected in multiple to an auxiliary voltage limiter, and means under the control of said auxiliary voltage limiter to vary said bias voltage.

WILLIAM I-I. T. HOLDEN.

REFERENCES CITED UNITED STATES PATENTS Name Date Hubbard July 22, 1941 Number 

